The essential amino acids Leucin, Isoleucin and Valin are called "branched chained amino acids" because of their chemical structure. The body cannot produce these amino acids and is therefore relying on external source.
BCAA's are important building blocks for the production of L-Glutamin and L-Alanin and therefore play an important rolse in the maintenance and building of muscle tissue. BCAA's should be taken immediately after an exercise regimen.